148 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pfeifer's Embryograph.* — This piece of apparatus, the work of Mr. 

 A. Pfeifer, the instrument-maker of the Biological Laboratory of the 



Johns - Hopkins University, Balti- 

 more, " renders the Zeiss-Oberhauser 

 camera available for drawing objects 

 under very low magnifying powers." 

 It consists, first, of a collar fitted 

 to the arm of the Microscope, and 

 furnished with a short draw-tube, 

 which can be placed with the objective 

 either above or below the arm ; and, 

 second, of a vertical rod, supported 

 on an arm which is clamped under 

 the collar of the draw-tube, and 

 carries a second movable arm resting 

 in a collar to support the camera. 

 This ai'm is held in place by a 

 thumb-screw, and it may be set at 

 any point on the vertical rod. When 

 the Zeiss aa objective is used, and 

 the camera is lowered as much as 

 possible, an image magnified about 

 three diameters is projected on the 

 paper, and any ami)lifi^cation greater 

 than three diameters may be ob- 

 tained by varying the height of the 

 camera, and by the use of the higher 

 objectives. 



Schott's Microscopes. — A matter that has long puzzled microscopists 

 has happily found a solution, and although the discovery is not calculated 

 to produce any revolution in microscopy, it is worthy of being recorded in 

 a microscopical journal. 



Gaspar Schott, in his ' Magia Universalis,'! figures and describes among 

 others the Microscopes shown in figs. 11, 12, and 13. These Microscopes, 

 as will be seen, are apparently of an exceptional and extraordinary size, and 

 no explanation is furnished by the text or otherwise of the advantages sup- 

 posed to be obtained by their large dimensions. So far as anything is known 

 of the ideas of Schott's contemporaries, there is nothing that in any way tends 

 to show that the uselessness of mere size was not thoroughly appreciated, so 

 far as Microscopes at any rate, in contradistinction to telescopes, are con- 

 cerned. Added to this, Schott himself writes of gold and silver dust, small 

 seeds, &c., being viewed by these Microscopes, objects which are obviously 

 unsuited for large instruments. As no reasonable explanation was forth- 

 coming, some microscopists fell back upon the notion that Schott was 

 drawing upon his imagination for the whole thing, and that no such Micro- 

 scopes had ever in fact been made. 



We recently received from Prof. Abbe, Traber's * Nervus Opticus,' J 

 and we happened to open it at the plate containing the three drawings 



* Stud. Biol. Laborat. Johns-Hopkins Univ., iii. (1886) pp. 480-1 (1 fig.). 



t G. Schott, ' Mugia Universalis naturaa et arlis. I. Magia Optica.' 4to, Herbipolis, 

 1657, pp. 533-G, pi. xxv. f5g8. 5, 7, and 8. 



X P. Trahcr, ' Nervus Opticus sive Tractatus Theoricus, in tres libros Opticani, 

 Catoptricaui Dioptricam distributus,' xiii. and 22(> pp. and 35 pis., i'ol., Vicmia> AustiisB, 

 1690. 



